(1) Field of the Invention
The present invention generally relates to a cooling system of an internal combustion engine, and more particularly to a cooling system for cooling a cylinder by means of a coolant which flows in a passage formed on an outer surface of a cylinder liner.
(2) Description of the Related Art
Japanese Laid-Open Utility Model Application No. 63-168242 discloses a cooling system for cooling an internal combustion engine by passing a coolant through a spiral or ring-shaped passage formed on an outer surface of a cylinder liner.
FIGS. 1A, 1B and 1C are plan, front, and side views of a conventional cylinder liner, respectively. A plurality of ring passages 11 are spaced apart from each other at equal intervals in an axial direction of a cylinder liner 10, and are formed on an outer surface of the cylinder liner 10. All the passages 11 are coupled to each other by means of connection passages 12 and 13 formed in the axial direction of the cylinder liner 10. A traverse-sectional area of the connection passage 12 is uniform at any point thereof, and a traverse-sectional area of the connection passage 13 is also uniform at any point thereof.
The coolant is poured into the cylinder liner 10 in the traverse direction via an inflow part 14, and distributed into the passages 11 via the connection passage 12. The cylinder is cooled while the coolant is flowing in the passages 11. Then, the coolant passes through the connection passage 13 and is output via an outflow part
The cooling system of the internal combustion engine is primarily intended to reduce a deformation of a cylinder (a variation in the cylinder bore) by uniformly cooling the entire cylinder bore. Generally, the cylinder has a thermal distribution varying in the axial direction thereof. More specifically, an upper portion of the cylinder has a high temperature, and a lower portion thereof has a low temperature. Hence, it is desired that the coolant be supplied to the cylinder liner 10 so that a flow rate change which matches the temperature distribution of the cylinder can be obtained. However, the conventional cooling system does not have a coolant flow-rate change that matches the temperature distribution of the cylinder.